Particle Detectors for Colliders Calorimeters Robert S. Orr University of Toronto

R.S. Orr 2009 TRIUMF Summer Institute  Layers of Detector Systems around Collision Point Generic Detector

Scintillators charged particle photons Charged particle passing through matter distorts atom molecule lattice Relaxation of distortion – light emitted Emitted photon may – excite another molecule Successive excitation & emission – different λ photons each step whole chain Very fast – good timing resolution

R.S. Orr 2009 TRIUMF Summer Institute Can be extremely efficient ~ 100 photoelectrons per cm. Spatial resolution ~ size of scintillator ~10s cm Scintillating fibres

R.S. Orr 2009 TRIUMF Summer Institute Why are scintillators transparent to emitted light? Stokes shift

R.S. Orr 2009 TRIUMF Summer Institute Wavelength Shifting

R.S. Orr 2009 TRIUMF Summer Institute number of stages Fast Low noise High gain Photomultiplier

R.S. Orr 2009 TRIUMF Summer Institute PM Sensitivity

R.S. Orr 2009 TRIUMF Summer Institute Modern Photodetectors Micro-channel plates Multi-anode pm Hybrid pm Visible light photon counters

R.S. Orr 2009 TRIUMF Summer Institute Electromagnetic Showers incident Converts to 2 electrons Each electrons will have emitted a brems photon of energy Now have 4 particles energy Number of particles after Average energy At the critical energy assume this is max depth shower grows as ln E linear energy measurement resolution improves with energy

R.S. Orr 2009 TRIUMF Summer Institute Monte Carlo Simulation of an EM Shower Calc Put b=0.5 Get a from

R.S. Orr 2009 TRIUMF Summer Institute “b” is sort of material independent

R.S. Orr 2009 TRIUMF Summer Institute Transverse Shower Profile Shower Broadens as it develops Pair Brems Compton Multiple Coulomb Moliére Radius Like radiation length, Moliére radius scales for different materials In terms of Moliére radius, shower width is roughly independent of material - 90% of energy in Shower Broadens as it develops dense central core spreading with depth

R.S. Orr 2009 TRIUMF Summer Institute Comparison of Hadronic & Electromagnetic Showers

R.S. Orr 2009 TRIUMF Summer Institute Hadronic Calorimeters Strong (nuclear) interaction cascade Similar to EM shower hadronic interaction length Shower length hadronic calorimeter nearly always sampling calorimeters Energy Resolution leakage of energy shower fluctuations invisible energy loss mechanisms

R.S. Orr 2009 TRIUMF Summer Institute Sampling Calorimeter

R.S. Orr 2009 TRIUMF Summer Institute Hadronic Lateral Shower Profile Fe Hadronic shower much broader than EM Mean hadronic versus MCS Fe

R.S. Orr 2009 TRIUMF Summer Institute Hadronic Shower Longitudinal Development ZEUS Uranium/Scint

R.S. Orr 2009 TRIUMF Summer Institute Lateral Scaling with Material 90% containment does not scale core scales

R.S. Orr 2009 TRIUMF Summer Institute Calorimeter Energy Resolution sampling and shower fluctuations number of samples energy energy deposited in a sampling step stochastic term

R.S. Orr 2009 TRIUMF Summer Institute Calorimeter Energy Resolution counting statics in sensor system this term is usually negligible e.g. # of photo-electrons in PM, ion pairs in liquid argon mean # of photo-electrons in PM per unit of incident energy shower leakage fluctuations – make calorimeter as deep as $$ allow

R.S. Orr 2009 TRIUMF Summer Institute Calorimeter Energy Resolution noise - detector or electronics increases with number of channels summed over -important for low level signal -liquid argon electronics -detector capacitance N channels with some intrinsic noise noise (energy) deposited energy behaviour

R.S. Orr 2009 TRIUMF Summer Institute Calorimeter Energy Resolution inter - calibration uncertainty of channels constant -constant in E spatial in-homogeneity of detector energy response fractional channel to channel gain uncertainty dead space temperature variation radiation damage all these influence spatial variation of effective energy response

R.S. Orr 2009 TRIUMF Summer Institute Calorimeter non-uniformity

R.S. Orr 2009 TRIUMF Summer Institute  Layers of Detector Systems around Collision Point Generic Detector

R.S. Orr 2009 TRIUMF Summer Institute Semi-empirical model of hadron shower development radiation length hadronic part electromagnetic part interaction length - significant amount of material in front of calorimeter (magnet coil etc.)

R.S. Orr 2009 TRIUMF Summer Institute More Rules of Thumb for the Hobbyist Shower maximum 95% Longitudinal containment 95% Lateral containment Mixtures in sampling calorimeters active + passive material

R.S. Orr 2009 TRIUMF Summer Institute Typical Calorimeter Resolutions Homogeneous EM (crystal, glass) CLEO, Crystal Ball, Belle, CMS..... Sampling EM (Pb/Scint, Pb/LAr) CDF, ZEUS, ALEPH, ATLAS..... Non-compensating HAD (Fe/Scint, Fe/LAr) CDF,ATLAS,H1, LEP = everyone Compensating HAD (DU/Scint) ZEUS, HELIOS

R.S. Orr 2009 TRIUMF Summer Institute Invisible Energy in Hadronic Showers

R.S. Orr 2009 TRIUMF Summer Institute Difference in Response to Electrons and Hadrons

R.S. Orr 2009 TRIUMF Summer Institute Effect of e/h on Energy Resolution Fe/Scint DU/Scint Resolution tail

R.S. Orr 2009 TRIUMF Summer Institute Effect of e/h on Linearity DU/Scint Fe/Scint

R.S. Orr 2009 TRIUMF Summer Institute

Weighting to Correct for e/h Energy resolution does not improve Weight down EM part of shower tune

R.S. Orr 2009 TRIUMF Summer Institute Jet Energy Resolution Fluctuations between EM and Hadronic component in jets will degrade the energy resolution for jets Jet-jet Mass Resolution Effects other than e/h dominate the 2- jet mass resoluton

R.S. Orr 2009 TRIUMF Summer Institute Jet-Jet Mass Resolutions

R.S. Orr 2009 TRIUMF Summer Institute Conceptual Readout Schemes

R.S. Orr 2009 TRIUMF Summer Institute ZEUS Forward Calorimeter

R.S. Orr 2009 TRIUMF Summer Institute

 Layers of Detector Systems around Collision Point Generic Detector

LAr Calorimetry SM Higgs Discovery Potential Five different detector technologies Calorimetry coverage to EM Calorimeter WW Fusion Tag jets in Forward Cal EM Calorimeter Hadronic & Forward Calorimeters

Design Goals Technology EM Calorimeters ( ) and Presampler ( ) Hadronic Endcap ( ) Forward Calorimeter ( ) LAr Calorimeter Technology Overview Lead/Copper-Kapton/Liquid Argon Accordion Structure Copper/Copper-Kapton/Liquid Argon Plate Structure Tungsten/Copper/Liquid Argon Paraxial Rod Structure

LAr and Tile Calorimeters Tile barrelTile extended barrel LAr forward calorimeter (FCAL) LAr hadronic end-cap (HEC) LAr EM end-cap (EMEC) LAr EM barrel

R.S. Orr 2009 TRIUMF Summer Institute Electromagnetic Barrel Barrel Module Schematic with presampler 64 gaps /module 2.1 mm gap 2x3100 mm long Half Barrel Assembly 2x16 modules I.R/O.R 1470/2000 mm longitudinal samples presampler

R.S. Orr 2009 TRIUMF Summer Institute Electromagnetic Endcap 96 gaps /module outer wheel 32 gaps/module inner wheel mm gap outer mm inner 2x8 modules Diam mm longitudinal samples Front sampling of 6 for,  - strips.

R.S. Orr 2009 TRIUMF Summer Institute Accordion Structure Pb Absorber Honeycomb spacer & Cu/Kapton electrode

R.S. Orr 2009 TRIUMF Summer Institute Prototype of EM endcap Detail of Kaptons

R.S. Orr 2009 TRIUMF Summer Institute ATLAS FCAL

Pictures of assembly process

LAr Forward Calorimeters FCAL C assembly into tube – Fall 2003

R.S. Orr 2009 TRIUMF Summer Institute ATLAS HEC Structure

Hadronic Endcap Calorimeter (HEC) Composed of 2 wheels per end Front wheel: 67 t 25 mm Cu plates Back wheel: 90 t 50 mm Cu plates Rear Wheel Wheel Assembly Front Wheel

Oct 2002

Electromagnetic Endcap

Hadronic Endcap

HEC – FCAL Assembly

Lar Endcap Installed in ATLAS